[SCHEDULE 13D] GRAN TIERRA ENERGY INC. SEC Filing

Rhea-AI Filing Summary

Equinox Partners and affiliated funds report a 14.4% stake in Gran Tierra Energy (GTE). The filing states the Reporting Persons collectively beneficially own 5,097,688 shares out of 35,290,955 outstanding, based on the issuer's July 31, 2025 report. The positions were acquired with client investment capital totaling approximately $34,577,851, including commissions.

The group converted from a Schedule 13G to a Schedule 13D after Brad Virbitsky, an EPIM partner, was appointed an independent director effective 09/30/2025. The Reporting Persons say they consider the shares undervalued and retain flexibility to increase, decrease, or otherwise change their position, and may engage with management, other stockholders, or third parties about capital allocation, board composition, potential sales, or other strategic actions.

Positive

• Material stake of 14.4% gives meaningful influence without outright control
• Board representation via appointment of Brad Virbitsky effective 09/30/2025 provides direct engagement channel
• Transparent funding disclosure: approximately $34,577,851 used to acquire the positions

Negative

• No specific strategic proposals disclosed; intentions remain broadly stated and contingent
• Potential use of margin for client accounts introduces leverage-related constraints and risks
• Concentrated ownership may raise governance tensions with other shareholders if activist actions are proposed

Insights

Shareholder Activism Advisor

Large passive stake plus board seat signals potential active engagement.

The combination of a 14.4% economic stake and the appointment of an EPIM partner to the board creates a direct governance channel. That board presence converts a prior passive ownership profile into one with potential influence on strategy.

Risks include limited disclosed plans beyond monitoring and conventional engagement; material actions would require further disclosures. Watch for follow-up communications, proposals, or transactions over the next 3–12 months.

Portfolio Manager

Position size is material but not controlling; liquidity and funding noted.

The reported aggregate cost basis is about $34.6M for 5.1M shares, implying a meaningful but non-controlling 14.4% holding. Source of funds is client capital with potential margin use; positions may be adjusted subject to fund mandates and market conditions.

Investors should monitor share-count disclosures and any purchases/sales; the filing notes no transactions in the last 60 days, so trading activity announcements would be informative in the near term.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

GRAN TIERRA ENERGY INC.

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

38500T200

(CUSIP Number)

Eric Wagner
500 Fifth Avenue,
New York, NY, 10110
(212) 880-9845

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

09/30/2025

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 38500T200

1

Name of reporting person

Equinox Partners Investment Management LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 5,097,688.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 5,097,688.00

11

Aggregate amount beneficially owned by each reporting person

5,097,688.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

14.4 %

14

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person:

Includes 2,051,427 shares of Common Stock, par value $0.001 per share (the "Shares") of Gran Tierra Energy Inc. (the "Issuer") held in one or more client accounts over which Equinox Partners Investment Management LLC, as investment advisor, has shared voting and dispositive power. The filing of this statement should not be deemed as admission that Equinox Partners Investment Management LLC is, for the purposes of Section 13 of the Act, the beneficial owner of the Shares held in such client account(s).

SCHEDULE 13D

CUSIP No. 38500T200

1

Name of reporting person

Equinox Partners, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 2,163,682.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 2,163,682.00

11

Aggregate amount beneficially owned by each reporting person

2,163,682.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

6.1 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 38500T200

1

Name of reporting person

Kuroto Fund LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 538,700.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 538,700.00

11

Aggregate amount beneficially owned by each reporting person

538,700.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

1.5 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 38500T200

1

Name of reporting person

Mason Hill Partners, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 343,879.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 343,879.00

11

Aggregate amount beneficially owned by each reporting person

343,879.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

1 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 38500T200

1

Name of reporting person

Sean M. Fieler

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 5,097,688.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 5,097,688.00

11

Aggregate amount beneficially owned by each reporting person

5,097,688.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

14.4 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person:

See Footnote 1 on page 2. The filing of this statement should not be deemed an admission that Mr. Fieler is, for the purposes of Section 13 of the Act, the beneficial owner of the Shares held in such client account(s).

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, par value $0.001 per share
(b)	Name of Issuer: GRAN TIERRA ENERGY INC.
(c)	Address of Issuer's Principal Executive Offices: 500 CENTRE STREET SE, CALGARY, CANADA (FEDERAL LEVEL) , T2G 1A6.
Item 1 Comment: This Statement on Schedule 13D (this "Schedule 13D") relates to the Common Stock, par value $0.001 per share (the "Shares") of Gran Tierra Energy Inc., a Delaware corporation (the "Issuer"), whose principal executive offices are located at 500 Centre Street S.E., Calgary, Alberta T2G 1A6, Canada.
Item 2.	Identity and Background
(a)	This Schedule 13D is being filed by (i) Equinox Partners Investment Management LLC, a Delaware limited liability company ("EPIM"), (ii) Equinox Partners, L.P., a Delaware limited partnership ("Equinox Partners"), (iii) Kuroto Fund LP, a Delaware limited Partnership, ("Kuroto"), (iv) Mason Hill Partners, LP, a Delaware limited partnership ("Mason Hill Partners"), and (v) Sean M. Fieler, a United States Citizen ("Mr. Fieler" and, together with EPIM, Equinox Partners, Kuroto, and Mason Hill Partners, the "Reporting Persons").
(b)	The principal business address for each of the Reporting Persons is Three Stamford Plaza, 301 Tresser Blvd, 13th Fl., Stamford, CT 06901.
(c)	EPIM's principal business is serving as an investment advisor to certain private investment funds, including Equinox Partners, Kuroto, Mason Hill Partners, and other client accounts. Each of Equinox Partners, Kuroto, and Mason Hill Partners is a private investment fund. Mr. Fieler owns a controlling interest in, and is the managing member of, EPIM
(d)	During the last five years, none of the Reporting Persons have: (i) been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors); or (ii) been party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(e)	During the last five years, none of the Reporting Persons have: (i) been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors); or (ii) been party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(f)	EPIM is a Delaware limited liability company. Equinox Partners is a Delaware limited partnership. Kuroto is a Delaware limited partnership. Mason Hill Partners is a Delaware limited partnership. Mr. Fieler is a citizen of the United States.
Item 3.	Source and Amount of Funds or Other Consideration
	All of the Shares to which this Schedule 13D relates were purchased using the investment capital of the applicable clients of EPIM. The aggregate amount of funds used for the purchase of the Shares held by the Reporting Persons is approximately $34,577,851, including commissions. The Reporting Persons may effect purchases of Shares through margin accounts maintained for EPIM's clients with prime brokers, which extend margin credit as and when required to open or carry positions in their margin accounts, subject to applicable federal margin regulations, stock exchange rules and such firms' credit policies. Shares may be held in margin accounts and may be pledged as collateral security for the repayment of debit balances in such accounts. Since other securities may be held in such margin accounts, it may not be possible to determine the amounts, if any, of margin used to purchase the Shares.
Item 4.	Purpose of Transaction
	The Reporting Persons purchased the Shares based on the Reporting Persons' belief that the Shares, when purchased, were undervalued and represented an attractive investment opportunity. Depending upon overall market conditions, other investment opportunities available to the Reporting Persons, and the availability of Shares at prices that would make the purchase or sale of Shares desirable, the Reporting Persons may endeavor to increase or decrease their position in the Issuer through, among other things, the purchase or sale of Shares on the open market or in private transactions or otherwise, on such terms and at such times as the Reporting Persons may deem advisable. Brad Virbitsky, a portfolio manager and partner at EPIM, was appointed to the Issuer's Board of Directors as an independent director, effective September 30, 2025, prompting the change from a 13G to a 13D filer. No Reporting Person has any present plan or proposal which would relate to or result in any of the matters set forth in Item 4(a) through (j) of this Schedule 13D except as set forth herein or such as would occur upon or in connection with completion of, or following, any of the actions discussed herein. The Reporting Persons intend to review their investment in the Issuer on a continuing basis. Depending on various factors including, without limitation, the Issuer's financial position and investment strategy, the price levels of the Shares, conditions in the securities markets and general economic and industry conditions, the Reporting Persons may in the future take such actions with respect to their investment in the Issuer as they deem appropriate including, without limitation, engaging in communications with management and the Board of Directors, engaging in discussions with stockholders of the Issuer or third parties, including potential acquirers and service providers, about the Issuer and the Reporting Persons' investment, making proposals to the Issuer concerning changes to the capital allocation strategy, capitalization, ownership structure, including a sale of the Issuer as a whole or in parts, Board of Directors structure (including Board of Directors composition) or operations of the Issuer, purchasing additional Shares, selling some or all of their Shares, engaging in short selling of or any hedging or similar transaction with respect to the Shares, or changing their intention with respect to any and all matters referred to in Item 4.
Item 5.	Interest in Securities of the Issuer
(a)	The aggregate percentage of Shares reported owned by the Reporting Persons is based upon 35,290,955 Shares outstanding, which is the total number of Shares outstanding as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on July 31, 2025. As of the date hereof, the Reporting Persons beneficially own an aggregate of 5,097,688 Shares, constituting approximately 14.4% of the outstanding Shares. See rows (11) and (13) of the cover pages to this Schedule 13D for the aggregate number of Shares and percentage of the outstanding Shares beneficially owned by each of the Reporting Persons. See rows (7) through (10) of the cover pages to this Schedule 13D, including the notes relating thereto, for the number of Shares as to which each Reporting Person has the sole or shared power to vote or direct the vote and the sole or shared power to dispose or to direct the disposition. The filing of this Schedule 13D shall not be deemed an admission that the Reporting Persons are, for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, the beneficial owners of any securities of the Issuer that he or it does not directly own. Each of the Reporting Persons specifically disclaims beneficial ownership of the securities reported herein that he or it does not directly own. The Reporting Persons expect that Mr. Virbitsky will be awarded certain securities of the Issuer as compensation for his serving as a member of the Issuer's Board of Directors.
(b)	See item 5(a) above.
(c)	The Reporting Persons have not entered into any transactions in Shares during the past sixty days.
(d)	No Person is known to the Reporting Persons to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, any Shares that may be beneficially owned by the Reporting Persons.
(e)	Not applicable.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Except as described above, the only agreement that the Reporting Persons have entered into is a joint filing agreement, dated as October 6, 2025, a copy of which is attached hereto as Exhibit 99.1 and is incorporated herein by reference.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 99.1 Joint Filing Agreement to Schedule 13D by and among Equinox Partners Investment Management LLC, Equinox Partners, L.P., Kuroto Fund LP, Mason Hill Partners, LP and Sean M. Fieler dated as of October 6, 2025.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Equinox Partners Investment Management LLC

Signature:	/s/ Sean M. Fieler
Name/Title:	Sean M. Fieler, Manager
Date:	10/06/2025

Equinox Partners, L.P.

Signature:	/s/ Sean M. Fieler
Name/Title:	Sean M. Fieler, Manager of Equinox Partners Investment Management LLC, the Investment Manager of Equinox Partners, L.P.
Date:	10/06/2025

Kuroto Fund LP

Signature:	/s/ Sean M. Fieler
Name/Title:	Sean M. Fieler, Manager of Equinox Partners Investment Management LLC, the Investment Manager of Kuroto Fund LP
Date:	10/06/2025

Mason Hill Partners, LP

Signature:	/s/ Sean M. Fieler
Name/Title:	Sean M. Fieler, Manager of Equinox Partners Investment Management LLC, the Investment Manager of Mason Hill Partners, LP
Date:	10/06/2025

Sean M. Fieler

Signature:	/s/ Sean M. Fieler
Name/Title:	Sean M. Fieler
Date:	10/06/2025

FAQ

What stake does Equinox Partners report in Gran Tierra Energy (GTE)?

The Reporting Persons collectively own 5,097,688 shares, representing approximately 14.4% of outstanding shares.

How much was spent to acquire the reported shares?

The aggregate capital used to purchase the shares was approximately $34,577,851, including commissions.

Why did the filing change from Schedule 13G to Schedule 13D?

The change was prompted by the appointment of Brad Virbitsky as an independent director effective 09/30/2025.

Do the Reporting Persons have immediate plans to sell or buy more GTE shares?

No specific buy/sell plans are disclosed; the Reporting Persons state they may increase or decrease their position depending on market conditions and other factors.

Have the Reporting Persons traded GTE shares in the last 60 days?

The filing states no transactions in GTE shares were entered into during the past 60 days.